1. Field of the Invention
The present invention relates to an operating method and an apparatus thereof. In particular, this invention provides an operating method for a large dimension plasma enhanced atomic layer deposition cavity and an apparatus thereof.
2. Description of the Related Art
Currently, the SiO2 layer in the gate port for thin-film-transistors (TFTs) is formed by the plasma enhanced CVD method or the thermal CVD method. While plate displays have become larger, the manufacturing temperature and the number of transistors used have both decreased, and the SiO2 layer in the gate port has become thinner. However, the required driving voltage for the SiO2 layer has risen and some problems have consequently come to the fore, such as high leakage current and lower element reliability. A high dielectric material atomic layer thin film made by the plasma enhanced atomic layer deposition (PEALD) uses a nano-thickness layer to cover a large dimension substrate. The plasma enhanced atomic layer deposition controls the high dielectric material nano-thin-film deposition with low manufacturing temperature, low pollution and precise atomic thickness. Due to the development of high efficiency materials and low voltage element structures, organic light emitting diodes (OLEDs) focus on the electrode interface. The buffer layer is made of material with several atomic layers of thickness. The thin-film is deposited by the atomic layer deposition method.
The plasma enhanced atomic layer deposition adopts a continuous bi-chemical reaction. The deposition of a chemical precursor will be self-limiting. Next, the ligand excision and the surface activation are processed by utilizing an ionic group and/or an atomic group produced from the plasma. At the first semi-reaction, the gaseous chemical precursor reacts with the surface functional group. The reaction is processed continuously until all of the surface functional group has been reacted and replaced. This is the self-limiting characteristic of the atomic layer deposition. The free radical of the ionic group and the atomic group coming from the plasma forms vaporizable particles and excises the surface ligand to reserve the desired deposition surface layer. When the free radicals of the atomic group make the surface activate, the ionic effect make the deposition thin film tighten and crystallize. So, the plasma enhanced atomic layer deposition has a faster reaction speed and a faster vaporized product excision than the atomic layer deposition (ALD) at a lower temperature.
Because the first semi-reaction is self-limiting, an atomic layer deposition formed at every cycle is expected if the ionic group and the atomic group do not suffer from deposition reaction product etching. In the micro electronic manufacturing process, the plasma enhanced atomic layer deposition is extensively applied to deposit high dielectric gate oxidation layer material, inert refractory metal, diffusion barrier, and seed and metal nitrides of adhesion layers.
The principle of the atomic layer deposition is to expose the substrate's surface that deposits a thin film to a plurality of precursors replacing each other in cycle and purging gas. The deposition speed of the thin film is determined by the replacement period. In a unit time, the greater the replacement speed, the greater the deposition speed. In order to increase the switching speed of the plurality of precursors in a large dimension plasma enhanced atomic layer deposition apparatus, the gas distributing pipes for the plurality of precursors and purge gas are installed in the large dimension cavity. Furthermore, the high speed valve of each gas distributing pipe is installed near the cavity. Therefore, the plasma enhanced atomic layer deposition apparatus can switch the precursors in high speed to speed up the thin film deposition speed. Because the plasma needs to be operated in a specified pressure to absorb the RF power effectively and transfer the gas into plasma, it is necessary to control the pressure in the large dimension plasma enhanced atomic layer deposition cavity. The quantity of the precursors needs to be reduced and the gas-flow of the exhaust pipe increases in a short time to draw out the gas that does not completely react quickly. The throttle valve of the prior art that is used to control the pressure cannot increase or decrease the gas-flow of the exhaust pipe in a timely manner.
U.S. Pat. No. 6,428,859, “Sequential method for depositing a film by modulated ion-induced atomic layer deposition (MII-ALD)”, belongs to Angstron Systems. Their method uses a showerhead partition to separate the plasma cavity and the manufacturing cavity. The precursor gas that needs to be ionized is introduced into the plasma cavity, is ionized by the plasma, is drawn out by a vacuum pump via the showerhead, and then spreads to the substrate's surface in the manufacturing cavity. The precursor gas that does not need to be ionized is introduced into the manufacturing cavity directly and reacts with the substrate's surface. Because the precursor gas needs to spread out over the plasma cavity and fill the manufacturing cavity so that a reaction occurs on the substrate's surface, the time required for spreading gas into the cavity becomes longer when the substrate's dimensions and the volume of the cavity increases.
T.W. patent 563,176, “A gas transmitting apparatus for atomic layer deposition” belongs to Applied Material. Their apparatus uses a manufacturing cavity of small volume to make the precursor gas quickly spread to the manufacturing cavity full.
T.W. patent 578,212, “Atomic layer deposition reactor” belongs to ASM. It adopts a thermal cracking and plasma enhanced method for the atomic layer deposition apparatus. According to the plasma source, the plasma enhanced is classified into a capacitor couple plasma source and a inductor couple plasma source. Each plasma source is classified into a far side plasma source and a near side plasma source depending upon whether the substrate is dipped into the plasma or not. However, every cavity has only one inlet extending from one side of the cavity to another side of the cavity. When the volume of the cavity increases, the time needed for spreading gas into the cavity full becomes longer and lowers the switching rate for the gas.
In the throttle valve of the prior art used for controlling the pressure, the pressure in the cavity can be measured by a capacitor pressure gauge when the pressure is controlled. Next, the measured pressure is transmitted to a pressure controller via a direct current signal. The pressure controller compares the pre-determined pressure with the measured pressure obtained from the capacitor pressure gauge to adjust the position of the throttle valve. Thereby, the pressure in the cavity is the same as the pre-determined pressure. The throttle valve has two kinds of operating methods. The first is the same as the operation of the gate valve. The valve intersects with the cross-section of the pipe to control the gas-flow of the pipe. This valve can be used for an exhaust pipe with a large bore and it is hermetically sealed. When the valve is fully closed, it is the same as the gate valve and does not suffer from the problem of gas-exhaust. The position of the valve is controlled by a servomotor or a step motor.
The other operation requires that a valve that has the shape of butterfly wings be rotated to adjust the position of the valve. It is called a butterfly valve. The butterfly valve comprises a rotatable valve and a servomotor or a step motor used for adjusting the position of the valve. The servomotor automatically adjusts the position of the valve to change the conductance of the throttle valve via an inputting voltage signal. Therefore, the efficiency of the exhaust gas for the total system is controlled and the purpose of automatically controlling the pressure is achieved. Furthermore, in order to reduce the consumption of the chemical precursor, Sundew Technologies Company introduced nitrogen or inert gas into the exhaust pipe when the chemical precursor is inputted to reduce the exhaust-gas quantity of the exhaust pipe. Therefore, the pressure of chemical precursor in the manufacturing cavity increases quickly and the deposition rate of the chemical precursor also increases. The gas introduced into the exhaust pipe is called a ballast gas. When the manufacturing cavity is purified, a purifying gas (such as nitrogen or inert gas) is introduced and the ballast gas is exhausted. The gas-flow in the exhaust pipe increases and the gas in the cavity is quickly exhausted in order to purify the cavity.
The merit of the above design is the structure is simple. Only the size of the pipe for the ballast gas needs to be increased and a pneumatic valve must be added. Thereby, the gas-flow in the exhaust pipe is reduced, the deposition rate of the chemical precursor is increased and the gas-flow in the exhaust pipe is recovered quickly. However, there are some drawbacks. First, additional inert or nitrogen gas is consumed in every deposition manufacturing process. Second, the pressure in the cavity cannot be controlled effectively. For using the plasma, if the pressure cannot be controlled effectively, the power rate of the RF cannot be inputted effectively and the plasma cannot be ignited. Third, the nitrogen atom may be merged into the thin film in the thin film deposition process and the characteristics of the atomic layer thin film will be affected. Therefore, this method is not suitable for being used in the plasma enhanced atomic layer deposition apparatus.